Apelin is associated with clinicopathological parameters and prognosis in breast cancer patients

Purpose Apelin has been shown to be a novel angiogenic factor in various cancers. However, there is limited information regarding the role of apelin in breast cancer. The aim of the present study is to examine associations between apelin, clinicopathological variables, and clinical outcome in breast cancer patients. Methods In this study, we began by investigating the apelin expression in breast cancer with long-term follow-up using immunohistochemistry. We then analyzed the relationship between apelin expression and microvessel density (MVD), lymphatic vessel density (LVD), lymph node status as well as other established clinicopathological parameters. The relationship between apelin expression and prognosis was also studied. In addition, we compared the apelin and its ligant APJ expression between 30 breast cancer samples and normal breast tissues adjacent to the breast tumors using western blot (WB) and RT-PCR. Results Apelin protein expression was detected in the cytoplasm of the breast carcinoma cells at various intensities. Apelin expression was positive in 59.2% (84/142) of the breast cancer patients and apelin expression was significantly correlated with tumor size ( p = 0.030), stage ( p = 0.000), histological type ( p = 0.009), MVD ( p = 0.000), LVD ( p = 0.000), and lymph node metastasis ( p = 0.041). Survival curves determined by the Kaplan–Meier method and univariate analysis demonstrated that high expression of apelin was associated with both worse disease-free survival ( p < 0.001) and overall survival ( p < 0.001). Interestingly, a significant difference in apelin and APJ expression by WB as well as RT-PCR was observed between normal breast tissues adjacent to the breast tumors and breast cancer tissues. Conclusions Our results showed apelin expression was associated with tumor size, stage, histological type, MVD, LVD, lymph node metastasis and poor prognosis. The presence of apelin may be a new prognostic factor and potential therapeutic target for breast cancer.